r - 在 R 中索引矩阵

Question

这里是 R 新手用户。所以我有一个格式如下的数据集:

    Date  Temp  Month
 1-Jan-90 10.56      1
 2-Jan-90 11.11      1
 3-Jan-90 10.56      1
 4-Jan-90 -1.67      1
 5-Jan-90  0.56      1
 6-Jan-90 10.56      1
 7-Jan-90 12.78      1
 8-Jan-90 -1.11      1
 9-Jan-90  4.44      1
10-Jan-90 10.00      1

在 R 语法中:

datacl <- structure(list(Date = structure(1:10, .Label = c("1990/01/01", 
  "1990/01/02", "1990/01/03", "1990/01/04", "1990/01/05", "1990/01/06", 
  "1990/01/07", "1990/01/08", "1990/01/09", "1990/01/10"), class = "factor"), 
      Temp = c(10.56, 11.11, 10.56, -1.67, 0.56, 10.56, 12.78, 
      -1.11, 4.44, 10), Month = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
      1L, 1L)), .Names = c("Date", "Temp", "Month"), class = "data.frame", row.names = c(NA, 
  -10L))

我想对特定月份的数据进行子集化，并对温度应用更改因子，然后保存结果。所以我有类似的东西

idx <- subset(datacl, Month == 1)  # Index
results[idx[,2],1] = idx[,2]+change  # change applied to only index values

但我不断收到类似的错误

Error in results[idx[, 2], 1] = idx[, 2] + change: 
  only 0's may be mixed with negative subscripts

任何帮助，将不胜感激。

Answer 1

首先，给变化因子一个值:

change <- 1

现在，这是创建索引的方法:

# one approach to subsetting is to create a logical vector: 
jan.idx <- datacl$Month == 1

# alternatively the which function returns numeric indices:
jan.idx2 <- which(datacl$Month == 1)

如果你只想要一月份的数据子集，

jandata <- datacl[jan.idx,]
transformed.jandata <- transform(jandata, Temp = Temp + change) 

要保留整个数据框，但只将变化因子添加到 Jan temps:

datacl$Temp[jan.idx] <- datacl$Temp[jan.idx] + change